**Friday 25 June 2021 - 7:30pm****Topic:** Space Rocks and Chaotic Orbits: & Could Earth have a hidden companion?**Speaker:** Ian Kemp, ICRAR, ASNSW**Venue:** ZOOM - Members will receive an email with a link to join the meeting**Abstract:** Nothing could be more boring than a rock going round in orbit for millions of years, right? Well as usual, Ian begs to differ, and will take you on a quick tour of some of the features of orbits that you may not have come across before.

The elliptical orbit under the influence of gravity was solved theoretically by Isaac Newton in the 1600s, and his equations are usually used today, to calculate orbits of planets, moons, comets, near-Earth asteroids, and spacecraft. There are only two slight problems - firstly, the equations cannot actually be solved if there are more than two bodies involved (which is usually the case, e.g. Earth-Moon-Spacecraft); and secondly the equations are actually incorrect anyway because they don’t include time dilation due to velocity and gravity. The only way to understand orbits long term is to use numerical modelling with a supercomputer.

In this talk we will quickly run through some of the consequences of the 'three body problem' and the limitations of Newton’s model of gravity. We’ll discuss orbit swaps, drastic variations in Earth’s orbit round the Sun, and the underlying chaotic nature of orbits in general. There are a number of ways in which objects can share an orbit, which opens up an interesting question ... could the Earth have a companion following us around the Sun? If so, how could it get there? And, if not, why not? Ian will outline some original research into whether there might be something very interesting lurking at one of the Earth-Sun Lagrange points.

As a finale we will look at orbits in the framework of general relativity - what would it be like to orbit a black hole? And it’s time to get real about GPS satellites.**Biography:** Ian Kemp started his professional life in academic research - with a degree, PhD and postdoc in Materials Science. He then went off to work in Industry and government for a while (25 years) before getting back to research and obtaining a Masters degree in Astronomy. He currently works as a research scientist at the International Centre for Radio Astronomy Research (ICRAR) in Perth - working partly on ‘big data’ (i.e., extremely big, massive data) and partly on astrophysics research. https://www.icrar.org/people/ikemp/

Event Date:

Friday, 25 June, 2021 - 19:30

Location:

Online meeting using ZOOM

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